A typical cellular wireless network includes a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which wireless communication devices (UEs), such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the base station.
In general, a cellular wireless network may operate in accordance with a particular air interface protocol or “radio access technology,” with communications from the base stations to UEs defining a downlink or forward link and communications from the UEs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE) or Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), and Global System for Mobile Communications (GSM), among others. Each protocol may define its own procedures for registration of UEs, initiation of communications, handoff between coverage areas, and functions related to air interface communication.
In accordance with the air interface protocol, each coverage area may operate on one or more carrier frequencies or “carriers.” More particularly, the base station that radiates to define a given coverage area may support one or more frequency bands, such as the 800 MHz band (one or more frequency ranges around 800 MHz), the 1.9 GHz band (one or more frequency ranges around 1.9 GHz), and the 2.5 GHz band (one or more frequency ranges around 2.5 GHz), and may provide service on one or more carrier frequencies within each supported band. In a frequency division duplex (FDD) arrangement, different frequencies are used for the downlink than the uplink. Whereas, in a time division duplex (TDD) arrangement, the same frequency is used for the downlink and uplink and is allocated over time among downlink and uplink communications.
On each carrier frequency in a coverage area, the coverage area may also define a number of air interface channels for carrying information between the base station and the UEs. These channels may be defined in various ways, such as through frequency division multiplexing, time division multiplexing, and/or code-division multiplexing, for instance. By way of example, each coverage area may define a pilot channel, reference channel or other resource on which the base station may broadcast a pilot signal, reference signal, or the like that UEs may detect as an indication of coverage and may measure to evaluate coverage strength. As another example, each coverage area may define an uplink control channel or other resource on which UEs may transmit control messages such as registration requests and access requests to the base station. And each coverage area may define a downlink control channel or other resource on which the base station may transmit control messages such as system information messages and page messages to UEs. Each coverage area may then define one or more traffic channels or other resources for carrying communication traffic such as voice data and other data between the base station and UEs.
When a UE first powers on or enters into coverage of the network, the UE may scan for and identify a strongest pilot or reference signal and may register with the network by transmitting a registration request or attach request to a base station providing that signal. This registration process may serve to notify the network of the UE's presence in a particular coverage area and to facilitate network authentication of the UE. Once registered, the UE may then operate in an idle mode or connected or active mode. In the idle mode, the UE monitors a downlink control channel to receive overhead information and to check for any page messages, and the UE may have no assigned traffic channel resources on which to engage in bearer communication. In the connected or active mode, on the other hand, the UE may have assigned traffic channel resources on which to engage in beacon communications.
As explained above, when the network has a communication (such as a voice call or other traffic) to provide to a UE that is registered with the network but is operating in the idle mode, the network may page the UE in an effort to then facilitate assigning traffic channel resources to the UE. In particular, the network may transmit on the downlink a page message addressed to the UE. Assuming the UE receives this page message, the UE may then transmit to the network a page response message on the uplink. And upon receipt of the page response message, the network may then assign traffic channel resources to the UE, for use to carry the communication, thus transitioning the UE to the connected or active mode in which the UE can engage in the communication.
Likewise, when an idle UE seeks to initiate a communication (such as to place a voice call or engage in other bearer communication), the UE may transmit on the uplink to the base station an access, origination, or connection request, and the network may then assign traffic channel resources to the UE for use to carry the communication, similarly transitioning the UE to a connected or active mode in which the UE can engage in the communication.